Turbine rotor

ABSTRACT

For restraining the vibration of turbine rotor blades, a turbine rotor embodying the present invention comprises devices for constituting some pairs of blade groups each composed of a plurality of the turbine rotor blades secured to a bucket cover and for reducing the existence of vibration modes by frictionally linking adjacent blade groups to each other.

United States Patent 091 1111 3,728,044

Fujita et al. 5] Apr. 17, 1973 TURBINE ROTOR [56] References Cited [75] Inventors: Isao Fujita; Katsuo Daibo; ltsuro UNlTEDSTATES PATENTS g f 2,310,412 2/1943 Flanders ..416/l90 2,610,823 9 1952 Knowlton.... ..4l6/l90 [73] Assignee: Hitachi, Ltd., Tokyo, Japan 2,942,843 6/1960 Sampson l ..416/ 190 2,971,743 2/1961 Welsh ..416/191 Filed: J 1971 3,396,905 8/1968 Johnson ..416/l90 [21] Appl. No.: 156,914

Primary ExaminerEverette A. Powell, Jr.

Att0rneyCraig, Antonelli, Stewart and Hill [30] Foreign Application Priority Data June 29, 1970 Japan ..45/56035 ABSTRACT For restraining the vibration of turbine rotor blades, a [52] US. Cl. ..416/l90, 416/191, 44ll66/ 159066 turbinc rotor embodying the present inventio-n 5 l 1 Int Cl F0 1d 2/ prises devices for constituting some pairs of blade groups each composed of a plurality of the turbine [581 Fleld of Search rotor blades secured to a bucket cover and for reducing the existence of vibration modes by 'frictionally linking adjacent blade groups to each other.

6 Claims, 12 Drawing Figures PATENTED APR 1 7 I973 SHEET 1 OF 4 FIG. 3

INVENTORS ISAO FUIITA KATsuo omao,

ITSURO AOKI SATOSHI NINON l YA BY Crc fiwtomQQ; 4 H-LQQ ATTORNEYS PATENTEDAPRI 11915 3'. 728.044

SHEET 2 OF 4 INVENTORS lsAo FUIITAKATSUO DAlBO n-suRo Aom SATOSHI NINOMIYA BY Gala QMtokaQQi H-Lm ATTORNEYS PATENTEB APR 1 H975 SHEET t [If 4 0 0 0 0 w w ,0, m

-/?0TA T/0/v SPEED OFROTOR (n p. s.)

INVENTORS ISAO FUJITA KATSUO DA! BO ITSURO AOKI SATOSH NI NONIYA BY QMtowzQQ; HULL ATTORNEYS TURBINE ROTOR The present invention relates to a method for restraining the vibration of the rotor blades and particularly of long turbine blades.

A steam turbine rotor is conventionally constituted by rotor blades inserted into a rotor disk, which rotor blades are connected to each other per a degree of four l rotor blades by the bucket covers or lacing wires so as to constitute the blade groups.

However, the conventional rotor blades constituted by these blade groups have various types of vibration modes, so that complicated vibration phenomena are caused. Further, the vibration frequency varies with centrifugal force due to the rotation of the turbinerotor and with fixed conditions, that is, when the vibration frequency becomes an integer multiple of the rotation speed of the turbine rotor, the rotor blades fall into a resonance condition to cause violent vibration so that the rotor blades receive high stress. Accordingly, the rotor blades must be designed such that this resonance point does not appear near the rated operating speed of the rotor. However, it is difficult to accomplish the vibration design of such turbine rotor blades, and a large sum of cost and a long time have been expended so as to develop long rotor blades. The reasons for the difficulty of this vibration design are due to the following points: I) there are many vibration modes and; (2) since there are cases where the range of the operating speed is required to be wide, it is difficult to avoid the above-mentioned resonance.

However, since, in recent years, a turbine is made to have such a large capacity as the single capacity thereof becomes 600 MW or 1,000 MW, the vibration design for long rotor blades becomes a problem which must be solved at any cost.

The primary object of the present invention is to reduce the vibration stress occuring in the turbine rotor blades and thereby to make the rotor blades long successfully. The second object of the present invention is to manufacture the vibration restraining device for the rotor blades, which vibration restraining device may reduce the vibration modes causing trouble and may easily avoid the resonance point even in the case where the operating speed of the turbine is required to have a wide range. The third object of the present invention is to obtain a method for installing the vibration restraining devices easily.

The turbine rotor embodying the present invention is characterized in that the vibration restraining device is held by the adjacent ends of bucket covers each fixing a plurality of rotor blades, and that the blade groups adjacent to each other are linked by friction force between the bucket covers and the vibration restraining device.

The present invention is illustrated, merely by way of example, in the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of the rotor blades installing the vibration restraining devices embodying the present invention;

FIG. 2 is a top view of the vibration restraining device;

FIG. 3 is a side view of the vibration restraining device;

FIG. 4 is a view of the vibration restraining device looking in the direction of the arrows IV IV of FIG.

l, which view shows the installation state of the vibration restraining device;

' FIG. 5 is a sectional view taken along the line V V of FIG. 4;

FIG. 6 is a sectional view along the line VI VI of FIG. 4;

FIG. 7 is a sectional view along the line VII VII of FIG. 4;

FIGS. 8d are views showing the vibration modes of the rotor blades; and

FIG. 9 is Campbell's diagram.

In general, the vibration occuring at the blade groups has the following vibration modes, that is, as shown in FIG. 8a, the tangential first order vibration T, caused by vibration occuring in the before and behind direction of a blade row; as shown in FIG. 8b, the axial first order vibration A caused by vibration occuring in an axial direction; as shown in FIG. 80, the axial second order vibration A and, as shown in FIG. 8d, the axial third order vibration A Further, the frequency varies with variations in centrifugal force caused by rotation and in the fixed condition. FIG. 9 called Cainpbells diagram represents the change of frequency during the rotation of the turbine rotor, in which diagram the rotation speed of the turbine rotor and the frequency of blade are plotted on an abscissa ad on an ordinate, respectively, and oblique lines indicate positions where the frequency consists with a multiple of the rotation speed of the turbine rotor. These oblique lines are sometimes called the steam stimulus lines, and the resonance conditions occur at the rotation speeds corresponding to the points where such steam stimulus lines and the lines of the frequency of the rotor blade intersect with each other. resonance phenomena, if the blade groups are constituted to have the long linking of rotor blades, vibration energy which each blade absorbs by exciting force is offset, so that it is apparent that the vibration energy becomes very small. In this case, if the best vibration proof effect is desired, it is advisable to use a blade group, what is called endless blade group, which is formed by linking all the rotor blades to each other. However, this endless blade group can not avoid stress caused by heat and centrifugal force occuring during the rotation of the turbine rotor.

Accordingly, in the present invention, the vibration stress of the rotor blades is reduced by providing the linking between the turbine blade groups so that a constitution enabled to reduce the vibration modes causing troublesome problems as to strength may be obtained. In this case, the blade groups adjacent to each other are linked by frictional force between the bucket covers and the vibration restraining device for rotor blades.

Since the linking of the blade groups each composed of a plurality of rotor blades is made long in such a manner that the whole circumference of the turbine rotor is made into two four groups or into one ring, A and A; which represent the axial vibrations as groups within the vibration modes shown in FIG. 8 result in disappearance. Also, since the exciting force effects positive and negative works so as to be balanced, the tangential vibration T does not bring about the resonance condition. Further, the vibration stress becomes very small because of damping effect due to the friction between the bucket covers and the vibra- In reference to such' tion restraining device for the rotor blades, so that the vibration stress becomes negligible. In other words, within the vibration modes shown in FIG. 8, T,, A and A becomes so small that these can be neglected with respect to the problem of strength. However, .A remains as the nodal vibration of the disk comprising the rotor blades, but the vibration stress with respect to A also becomes small because of the enlargement of damping effect caused by the friction force between the bucket covers and the vibration restraining device for the rotor blades.

In the following description, one embodiment of the present invention is explained on the basis of th drawings.

In FIG. 1, the rotor disk 1 is integral with main shaft 2, to the whole circumference of which disk 1 are secured the rotor blades 3. The bucket covers 4 are secured to the tips of the rotor blades 3 by tenons (not shown) for the purpose of the reinforcement of the rotor blades 3 ad the prevention of the leakage of steam from the tips. For example, as shown in the drawing, one turbine blade group consists of five rotor blades. The vibration restraining devices 5 for the rotor blades are inserted into gaps between the adjacent bucket covers 4 so as to link the adjacent blade groups, so that the whole circumference is formed into two four groups or one ring.

In FIGS. 2 and 3 showing the constitution of the vibration restraining device 5, a main body 11 has grooves 12 and 13 formed in both side faces of the main body and a circular aperture 14 formed at the central portion of the main body 11. A pin 15 exposing the cylindrical face thereof to both the grooves is inserted into the aperture 14, that is, the pin 15 is made to project a portion thereof into the grooves. As mentioned below, the projections 16 are engaged with notches respectively formed at the ends of the bucket covers. The main body 11 are provided with end portions 17 and 18 at both ends thereof, which end portions are adapted to be bent in order that the vibration restraining device may be unable to slip out as accompanied with the axial movement thereof. Two shallow grooves 19 and 20 are disposed at both sides of the aperture 14 so as to form portions to be caulked for holding down the pin 15.

In reference to FIG. 4 showing the installation state of the vibration restraining device, the ends 21 of the bucket covers are made to be of projection-shape, which adjacent ends 21 are opposed to each other with an oblique angle with respect to the axial direction. The bucket covers 4 are secured to the rotor blades by the tenons 6, and the vibration restraining device is inserted into the gap formed by the parallel faces of the ends 21 of the bucket covers. The faces of the notches formed at the ends 21 are made to oppose to the aper- 'a punch such that the pin 15 can not slip out, and the portions caulked are designated by the numeral 24. Then, the end portions 17 and 18 are inwardly bent in the same manner as the portions formed by the shallow frictionally linked by large friction force between the vibration restraining device and the ends 21 caused by the centrifugal force, so that the tangential first order vibration T the axial second .order vibration A and the axial third order vibration A; within the vibration modes may be restrained. If the vibration restraining device embodying the present invention are utilized at the last-stage of a low-pressure turbine and at the forward stages thereof, these devices become particularly advantageous. Further, since the analysis of the vibration characteristic of the long turbine blades becomes very easy, experimental researches which have been effected at a great expense are simplified, the substantial avoidance of vibration is achieved smoothly even in the case of the application of this device to actual manufactures.

In reference to the above-mentioned embodyment, although there are not provided fixed points between both the ends of the adjacent bucket covers and the vibration restraining device, it goes without saying that the same effect may be obtained by fixing one of the paired ends of the adjacent bucket covers to the vibration restraining device and by forming the above-mentioned constitution only between the other end of the adjacent bucket covers and saId vibration restraining device.

What is claimed is:

l. A turbine rotor composed of a main shaft transmitting power generated at a turbine, a rotor disk for connecting turbine rotor blades to the main shaft, bucket covers each tying a plurality of rotor blades together as a unit so as to constitute blade groups, and vibration restraining devices each for linking the adjacent bucket covers at their adjacent ends through portions of the device frictionally engaging with the adjacent ends of the bucket covers, allowing the circumferential movement of said bucket covers and frictionally linking the adjacent blade groups together at their adjacent ends, wherein each of the vibration restraining devices for the turbine rotor blades is composed of a main body having grooves formed in both side faces of the main body for engaging with adjacent ends of adjacent bucket covers and having an aperture formed at the central portion of the main body which communicates with both of the grooves, and a pin inserted into the aperture and made to project a portion thereof into said grooves so as to be engaged with notches respectively formed at the ends of the bucket covers, the main body having at both ends portions adapted to be bent after the installation of said main body in order that the main body may be unable to slip out as accompanied with the axial movement thereof.

2. A turbine rotor composed of a main shaft transmitting power generated at a turbine, a rotor disk for connecting turbine rotor blades to the main shaft, bucket covers each tying a plurality of rotor blades together as a unit so as to constitute blade groups, and vibration restraining devices each for linking the adjacent bucket covers at their adjacent ends through portions of the device frictionally engaging with the adjacent ends of the bucket covers, allowing the circumferential movement of said bucket covers frictionally linking the adjacent blade groups together at their adjacent ends, wherein each of the vibration restraining devices for the turbine rotor blades is composed of a main body having grooves formed in both side faces of the main body for engaging with adjacent ends of adjacent bucket covers and having an aperture formed at the central portion of the main body which communicates with both of the grooves, and a pin inserted into the aperture and made to project a portion thereof into said grooves so as to be engaged with notches respectively formed at the ends of the bucket covers, the main body having at both ends portions adapted to be bent after the installation of the main body in order that the main body may be unable to slip out as accompanied of the bucket covers each tying a plurality of rotor blades together as a unit so as to constitute blade groups, and that each of the vibration restraining devices linking the blade groups adjacent to each other is made to have an oblique angle with respect to the axial direction.

4. A turbine rotor according to claim 2, characterized in that each of the vibration restraining devices for the turbine rotor blades is held by the adjacent ends of the bucket covers each tying a plurality of rotor blades together as a unit so as to constitute blade groups, and that each of the vibration restraining devices linking the blade groups adjacent to each other is made to have an oblique angle with respect to the axial direction.

5. A turbine rotor according to claim 1, wherein the frictionally engaging portion of the devices include means for restraining each vibration of the tangential axial first (T second (T and third (T order vibrations of the rotor and blade assembly.

6. A turbine rotor according to claim 2, wherein the frictionally engaging portion of the devices include means for restraining each vibration of the tangential axial first (T second (T and third (T order vibrations of the rotor and blade assembly. 

1. A turbine rotor composed of a main shaft transmitting power generated at a turbine, a rotor disk for connecting turbine rotor blades to the main shaft, bucket covers each tying a plurality of rotor blades together as a unit so as to constitute blade groups, and vibration restraining devices each for linking the adjacent bucket covers at their adjacent ends through portions of the device frictionally engaging with the adjacent ends of the bucket covers, allowing the circumferential movement of said bucket covers and frictionally linking the adjacent blade groups together at their adjacent ends, wherein each of the vibration restraining devices for the turbine rotor blades is composed of a main body having grooves formed in both side faces of the main body for engaging with adjacent ends of adjacent bucket covers and having an aperture formed at the central portion of the main body which communicates with both of the grooves, and a pin inserted into the aperture and made to project a portion thereof into said grooves so as to be engaged with notches respectively formed at the ends of the bucket covers, the main body having at both ends portions adapted to be bent after the installation of said main body in order that the main body may be unable to slip out as accompanied with the axial movement thereof.
 2. A turbine rotor composed of a main shaft transmitting power generated at a turbine, a rotor disk for connecting turbine rotor blades to the main shaft, bucket covers each tying a plurality of rotor blades together as a unit so as to constitute blade groups, and vibration restraining devices each for linking the adjacent bucket covers at their adjacent ends through portions of the device frictionally engaging with the adjacent ends of the bucket covers, allowing the circumferential movement of said bucket covers frictionally linking the adjacent blade groups together at their adjacent ends, wherein each of the vibration restraining devices for the turbine rotor blades is composed of a main body having grooves formed in both side faces of the main body for engaging with adjacent ends of adjacent bucket covers and having an aperture formed at the central portion of the main body which communicates with both of the grooves, and a pin inserted into the aperture and made to project a portion thereof into said grooves so as to be engaged with notches respectively formed at the ends of the bucket covers, the main body having at both ends portions adapted to be bent after the installation of the main body in order that the main body may be unable to slip out as accompanied with the axial movement thereof and shallow grooves disposed at both sides of the aperture so as to form portions to be caulked for holding down the pin.
 3. A turbine rotor according to claim 1, characterized in that each of the vibration restraining devices for the turbine rotor blades is held by the adjacent ends of the bucket covers each tying a plurality of rotor blades together as a unit so as to constitute blade grOups, and that each of the vibration restraining devices linking the blade groups adjacent to each other is made to have an oblique angle with respect to the axial direction.
 4. A turbine rotor according to claim 2, characterized in that each of the vibration restraining devices for the turbine rotor blades is held by the adjacent ends of the bucket covers each tying a plurality of rotor blades together as a unit so as to constitute blade groups, and that each of the vibration restraining devices linking the blade groups adjacent to each other is made to have an oblique angle with respect to the axial direction.
 5. A turbine rotor according to claim 1, wherein the frictionally engaging portion of the devices include means for restraining each vibration of the tangential axial first (T1), second (T2), and third (T3) order vibrations of the rotor and blade assembly.
 6. A turbine rotor according to claim 2, wherein the frictionally engaging portion of the devices include means for restraining each vibration of the tangential axial first (T1), second (T2), and third (T3) order vibrations of the rotor and blade assembly. 